Light circuit buzz on DCC tracks

[ksxmi]

I have a Koki 107 with taillight and a Yo 5000 (also with directional taillight).

 

They are fine on a DC tracks, but when i run them on a DCC layout, there is an audible buzz coming out from these 2 cars.

 

I took apart both of them and noticed there is a 561 or 195 chip, can someone enlighten me what this chip function is?

 

When I power the car with e 9V battery, the led voltage was around 1.2V (I don't have a good steady hand to hold onto the led ends, but I wasn't able to see the same 9V on the LED) I suspect that chip must have drop the voltage?

I don't have enough alligator clips to test the LED voltage on the DCC tracks, and I am also unable to find an similar scenario on the internet.
 

[cteno4]

That’s a 561 ohm SMD resistor. I’m guessing something is humming from dcc digital oscillation.

 

jeff